1. Field of the Invention
The present invention relates to a styrene resin composition, particularly to a styrene resin composition comprising a styrene polymer having an atactic structure (hereinafter referred to as an xe2x80x9catactic polystyrene,xe2x80x9d or abbreviated as APS), or a styrene polymer having an atactic structure and a rubber-like elastic substance; a styrene polymer predominantly having a specific syndiotactic structure (hereinafter referred to as a xe2x80x9csyndiotactic polystyrene, or abbreviated as SPS); and, optionally a specific polyphenylene ether (hereinafter abbreviated as PPE); or, an inorganic filler. The present invention also relates to a method of manufacturing the same, and a method of manufacturing styrene resin molded products.
2. Description of the Related Art
Conventionally, APS resins manufactured through radical polymerization have been widely used, because they are inexpensive. However, their atactic steric structure makes APS resins amorphous, thereby imparting unsatisfactory solvent resistance to APS resins. As a result, APS resins have been applicable only to a limited use of material.
In order to overcome such poor solvent resistance, styrene has been copolymerized with a polar monomer such as acrylonitrile, methacrylate, acrylate, maleic anhydride, or maleimide. However, these copolymers have drawbacks in that their copolymerization ratio is limited, their productivity is low, their color is unsatisfactory, they generate unpleasant smell, and recycling is difficult when they are mixed with other polystyrene resins.
Crystalline syndiotactic polystyrene resins have been developed and there have been proposed compositions wherein a syndiotactic polystyrene resin is incorporated in the resin composition of a thermoplastic resin so as to improve its heat resistance (Japanese Patent Application Laid-Open (kokai) Nos. 62-104818, 62-257948, 62-257950, 1-182344). Blending a syndiotactic polystyrene resin with an atactic polystyrene resin improves heat resistance, but does not endow the molded products with satisfactory solvent resistance or impact resistance.
In view of the foregoing, the present inventors have conducted extensive studies and found that simply blending an SPS having a specific melting point with an APS resin followed by an optional addition of a polyphenylene ether having a specific intrinsic viscosity permits kneading and molding at a temperature which can minimize heat deterioration of APS, and improves moldability and solvent resistance of the resin composition without its impact resistance being deteriorated. The inventors have also found that incorporating an inorganic filler in a predetermined amount allows further improvement of heat resistance and elastic modulus of the resin composition. Moreover, the inventors have found that kneading of each of the components of the resin composition and molding at temperatures falling within a specific temperature range enables efficient manufacture of the resin composition of the present invention and molding thereof. The present invention has been completed based on these findings.
Accordingly, an object of the present invention is to provide an APS resin composition having improved solvent resistance without use of any special compatibility-enhancing agent and having excellent moldability and impact resistance.
Another object of the present invention is to provide a method of manufacturing said APS composition.
Still another object of the present invention is to provide a method of manufacturing APS resin molded products.
In one aspect of the present invention, there are provided following styrene resin compositions;
(1) A styrene resin composition which comprises the following components (A), and (B):
(A) a styrene polymer having an atactic:
30 to 95 weight %; and
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure:
70 to 5 weight %;
(2) A styrene resin composition which comprises the following components (A), and (B):
(A) a styrene polymer having an atactic structure and containing a rubber-like elastic substance:
30 to 95 weight %; and
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 weight %;
(3) A styrene resin composition which comprises the following components (A), (B), and (C):
(A) a styrene polymer having an atactic structure or a styrene polymer having an atactic structure and containing a rubber-like elastic substance: 30 to 95 parts by weight;
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 weight %; and
(C) a polyphenylene ether having an intrinsic viscosity of 0.5 deciliter/g or less measured in chloroform at 25xc2x0 C. in an amount of 1 to 100 parts, preferably 1 to 20 parts, by weight with respect to 100 parts by weight in total of component (A) and component (B);
(4) A styrene resin composition which comprises the following components (A), (B), and (D):
(A) a styrene polymer having an atactic structure or a styrene polymer having an atactic structure and containing a rubber-like elastic substance: 30 to 95 parts by weight;
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 parts by weight; and
(D) an inorganic filler in an amount of 1 to 70 weight % with respect to total weight of the resin composition.
(5) A styrene resin composition which comprises the following components (A), (B), (D), and (E):
(A) a styrene polymer having an atactic structure or a styrene polymer having an atactic structure and containing a rubber-like elastic substance: 30 to 95 parts by weight;
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 parts by weight;
(D) an inorganic filler in an amount of 1 to 70 weight % with respect to total weight of the resin composition; and
(E) a polymer having compatibility or affinity with components (A) and (B) and having a polar group in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight in total of components (A), (B), and (C).
(6) A styrene resin composition which comprises the following components (A), (B), (C), and (D):
(A) a styrene polymer having an atactic structure or a styrene polymer having an atactic structure and containing a rubber-like elastic substance: 30 to 95 parts by weight;
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 parts by weight;
(C) a polyphenylene ether having an intrinsic viscosity of 0.5 deciliter/g or less measured in chloroform at 25xc2x0 C. in an amount of 1 to 100 parts by weight with respect to 100 parts by weight in total of component (A) and component (B); and
(D) an inorganic filler in an amount of 1 to 70 weight % with respect to total weight of the resin composition.
(7) A styrene resin composition which comprises the following components (A), (B), (C), (D), and (E):
(A) a styrene polymer having an atactic structure or a styrene polymer having an atactic structure and containing a rubber-like elastic substance: 30 to 95 parts by weight;
(B) a styrene polymer having a melting point of not higher than 255xc2x0 C. and having predominantly a syndiotactic structure: 70 to 5 parts by weight;
(C) a polyphenylene ether having an intrinsic viscosity of 0.5 deciliter/g or less measured in chloroform at 25xc2x0 C. in an amount of 1 to 100 parts by weight with respect to 100 parts by weight in total of component (A) and component (B);
(D) an inorganic filler in an amount of 1 to 70 weight % with respect to total weight of the resin composition; and
(E) a polymer having compatibility or affinity with components (A) and (B) and having a polar group in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight in total of components (A), (B), and (C).
In another aspect of the present invention, there is provided a method of producing the styrene resin composition mentioned in the above aspect (1) through (7), which method comprises kneading the respective components within a resin temperature range between the melting point of component (B) and 27xc2x0 C. inclusive.
In yet another aspect of the present invention, there is provided a method of manufacturing styrene resin molded products through use of the styrene resin composition mentioned in the above aspect (1) through (7), which method comprises molding a composition within a resin temperature range between the melting point of component (B) and 270xc2x0 C. inclusive as measured during molding.